Semiconductor device

ABSTRACT

A chip size package semiconductor device can have reliable solder mounting and improved mounting reliability. A semiconductor device ( 10 ) of one embodiment can include a semiconductor chip ( 1 ) mounted to a bottom portion ( 11 ) of a metal base ( 10 ). A metal base ( 10 ) can have side portions ( 12 ) with connection electrodes ( 15 ) having a surface level higher than that of electrodes ( 7  and  8 ) on a surface of the semiconductor chip ( 1 ) by a difference (d). The semiconductor device ( 10 ) can be mounted face down without abutting the semiconductor chip ( 1 ) against a mounting substrate, thereby preventing mechanical damage to a semiconductor chip ( 1 ). At the same time, a solder layer can be formed in the gap between electrodes ( 7  and  8 ) and the mounting substrate, thereby raising the reliability of the soldering connection.

This application is a divisional of patent application Ser. No.10/611,903 filed Jul. 3, 2003.

TECHNICAL FIELD

The present invention relates generally to a semiconductor devicepackaging, and more particularly to a chip-size package for asemiconductor device.

BACKGROUND OF THE INVENTION

There continues to be a demand for a higher degree of integration forelectronic devices that mount semiconductor devices. To meet such goals,there has been a corresponding demand for the reduction in the size ofindividual semiconductor device packages. One type of semiconductordevice package that has been proposed is the “chip size package (CSP)”.

FIG. 12 shows a semiconductor device disclosed in U.S. PatentApplication Publication 2001/00048116 A1. In this device, a metal plateis provided that is slightly larger than a semiconductor chip 101. Themetal plate is processed to have a dish-like shape (e.g., a recessedportion) and the semiconductor chip 101 is mounted in a concave portion111 of the metal plate (hereinafter referred to as metal base 110).

A semiconductor chip 101 in this example is a metal-oxide-semiconductor(MOS) transistor chip. A drain electrode (not shown) is formed on therear surface of the semiconductor chip 101 and is fixed directly to thebottom surface of the concave portion 111. The space surrounding thesemiconductor chip 101 in the concave portion 111 is filled with a resin113 for sealing. A gate electrode 107 and a source electrode 108 areformed on the surface of the semiconductor chip 101 to be coplanar withthe surface of the metal base 110. Regions within a peripheral portion112 on the surface of the metal base 110 serve as drain connectionelectrodes 115.

The semiconductor device is mounted face down onto a mounting substrate(not shown in the drawing) so that drain connection electrodes 115 inperipheral portions 112 of metal base 110 are connected to drainconnection electrode pad portion provided on the mounting substrate. Atthe same time, the gate electrode 107 and source electrode 108 areconnected to a gate electrode pad portion and source electrode padportion (also not shown in the drawing).

The above publication also proposes, as shown in FIG. 13(a), a structurein which a concave portion 121 is formed leaving portions 122 on bothsides of a metal base 120. The surfaces of both side portions 122 areused as drain electrodes 125. In addition, as shown in FIG. 13(b), thepublication shows a structure in which, instead of both side portions,one side portion 132 of a metal base 130 is left to form a concaveportion 131. Grooves 133, as deep as the entire thickness of the metalbase 130, are formed in several locations along the length of the oneside portion 132. The surfaces of the regions separated by grooves 133are used as drain electrodes 135.

A technique similar to the one shown in FIG. 13(a) is disclosed inJapanese publication 08-78657 A (the illustration of which is notincluded herein). In this technique, a concave portion is formed leavingboth side portions. A semiconductor chip is mounted in the concaveportion. The device is mounted face down, with the surfaces of both sideportions being coplanar with electrodes on the surface of thesemiconductor chip.

U.S. Pat. No. 6,133,634 discloses a semiconductor device that is almostidentical to the semiconductor device shown in FIG. 14. In thissemiconductor device, a metal base 140 receives press work, or the like,to form a concave portion 141 and leaving a peripheral portion 142. Asemiconductor chip 101 is fixed in the concave portion 141. The surfaceof the peripheral portion 142 of the metal base 140 is substantiallycoplanar with electrodes 102 that are formed on the semiconductor chip101. Solder balls 103 are formed on the surface of the peripheralportion 142 and on the electrodes 102 on the surface of thesemiconductor chip 101. This device is mounted face down.

In the above conventional devices, the metal base is slightly larger insurface area than the semiconductor chip, and the total thickness is thesum of the thickness of the semiconductor device and the thickness ofthe metal base (at the bottom of a concave portion). Furthermore, thereis no need to bond a metal wire, or the like, to the semiconductordevice, and resin is not necessary for sealing the package. This makesit possible to reduce the size and thickness of a semiconductor devicechip holding package. Further, such a relatively simple structure can beeasy to manufacture. Another advantage can be heat dissipation. Whensuch structures are mounted, the metal base can function as a heat sink,thereby dissipating heat.

However, inspections by the inventors of the present invention arebelieved to show latent problems inherent in the above structures. In adevice in which a concave portion is formed that leaves a peripheralportion of a metal base, such as that of FIGS. 12 and 14, such a concaveportion is obtained through press work or etching of the metal base.Finishing a device with such a relatively complicated process can makeit difficult to form a desired shape with a high degree of precision.Thus, such metal base forming techniques present an obstacle to costreduction. The semiconductor devices shown in FIGS. 13(a) and 13(b) aresuperior in this regard (i.e., size and/or cost reduction), because bothside portions (or one side portion) can be formed by bending or cutting.Thus, achieving higher processing precision can be relatively easy.Additionally, such approaches can have improved heat dissipationcapabilities and improved mechanical strength, despite being smallerand/or thinner.

However, in a semiconductor device like that of FIG. 13(a), a drainconnection electrode 125 has a larger area than the gate electrode 107and source electrode 108, because the side portions 122 of metal base120 have flat surfaces and the entirety of the flat surfaces are used toform the drain connection electrode 125. This means that when the deviceis mounted face down, the heat capacity of the drain connectionelectrode 125 is larger than that of the gate electrode 107 and sourceelectrode 108. Therefore, it can be necessary to supply a larger amountof solder to drain connection electrodes 125 than the solder amount forgate electrode 107 and source electrode 108 when mounting the device toa mounting substrate with solder. As a result, the solder density on themounting substrate can be uneven. Further, heat capacitance of thesolder is irregular.

Accordingly, higher temperatures at the drain electrodes 125 can benecessary during a solder reflow step, and such a higher temperature canbring thermal damage to a part of the semiconductor device. Inparticular, damage may occur at a portion where the semiconductor chipis connected to the metal base. Further, such higher temperatures canreduce the reliability of a connection to gate electrode 107 and sourceelectrode 108 when the solder amount is low. This can ultimately lowerthe reliability of the mounting.

Another drawback to an approach like that of FIG. 13(a) can be thesubstantially coplanar arrangement of the drain connection electrodes125 with the surfaces of the gate electrode 107 and the source electrode108. When the semiconductor device is mounted face down onto themounting substrate, the gate electrode 107 and source electrode 108 cancollide against the surface of the mounting substrate, and causemechanical damage to such electrodes and/or to other parts of thesemiconductor chip 101.

It is noted that the semiconductor devices like those shown in FIGS. 12and 14 can be subject to the same above drawbacks, as the drainconnection electrodes for such structures like that of FIG. 13(a).

Similarly, the semiconductor device shown in FIG. 13(b) includes a drainconnection electrode 135 having a larger area than a gate electrode orsource electrode. The device thus suffers from similar problems,including varying solder amounts, arising from variances in heatcapacity, accompanying thermal damage, and lowered reliability in asolder connection.

If drain connection electrodes 135 are reduced in area, heat capacity ofthe individual drain connection electrodes during a mounting process canbe reduced, and can address the above drawbacks. However, drainconnection electrodes 135 are in regions separated by grooves 133 asdeep as the entire metal base 130. Thus, in order to separate drainconnection electrodes 135, each of the drain connection electrodes 135would be cantilevered with respect to the metal base 130. This can lowerthe mechanical strength of the drain connection electrodes 135 andweakens the metal base supporting strength when the device is mounted onthe mounting substrate. Thus, such a modification can present anotherfactor to lower the mounting reliability.

Still further, like the device of FIG. 13(a), in the device of FIG.13(b) drain connection electrodes 135 can have a surface essentiallylevel with that of the gate electrode 107 and source electrode 108.Thus, an approach like that of FIG. 13(b) can also suffer frommechanical damage when mounting takes place.

In light of the above, it would be desirable to arrive at asemiconductor device having an improved mounting reliability withrespect to conventional approaches. In particular, it would be desirableto arrive at such a result by improving soldering upon mounting such adevice.

SUMMARY OF THE INVENTION

The present invention can include a semiconductor device having a metalbase with a bottom portion formed from a metal plate and at least oneconnection electrode that extends upward from at least a part of thebottom portion to a first surface level. The at least one connectionelectrode is for mounting the semiconductor device to a mountingsurface. The semiconductor device also includes a semiconductor chipmounted to the bottom portion of the metal base having a surface withsurface electrodes at a second surface level. The first surface level ishigher than the second surface level by a predetermined amount. Thesurface electrodes are also for mounting the semiconductor device to themounting surface.

According to one aspect of the embodiments, the predetermined amount canbe greater than 0 millimeters and less than or equal to 0.1 mm.

According to another aspect of the embodiments, a semiconductor devicecan also include solder balls formed on at least one of the connectionelectrodes and one of the surface electrodes.

According to another aspect of the embodiments, a semiconductor chip canbe an insulated gate field effect transistor (IGFET) having a drainelectrode formed on a rear surface in direct electrical contact with thebottom portion of the metal base. Thus, the at least one connectionelectrode can be a drain connection electrode. The surface electrodescan include a gate electrode and source electrode for the IGFET.

The present invention can also include a semiconductor device with ametal base having a bottom portion formed from a metal plate and atleast two side portions situated upward from the bottom portion. The atleast two side portions can have notches therein to form upper and loweredges in the side portions. The upper edges can be connection electrodesfor mounting the semiconductor device to a mounting surface. Thesemiconductor device can also include a semiconductor chip mounted tothe bottom portion of the metal base having a surface with surfaceelectrodes for mounting the semiconductor device to the mountingsurface.

According to one aspect of the embodiments, each of the connectionelectrodes can have an area that is less than any of the surfaceelectrodes.

According to another aspect of the embodiments, connection electrodescan be symmetrical about a first axis that is parallel to the sideportions, and symmetrical about a second axis that is perpendicular tothe first axis.

According to another aspect of the embodiments, a metal base can includegrooves along a border between the bottom portion and each side portion.

According to another aspect of the embodiments, upper edges of sideportions can be bent outward, away from remaining portions of thecorresponding side portion.

The present invention can also include semiconductor device with a metalbase having a bottom portion formed from a metal plate and at least oneconnection electrode for mounting the semiconductor device to a mountingsurface. The at least one connection electrode can extend upward fromthe bottom portion and can be formed from portions of the metal platethat are thicker than remaining portions. The semiconductor device canalso include a semiconductor chip mounted to the bottom portion of themetal base having a surface with surface electrodes for mounting thesemiconductor device to the mounting surface. The area of the connectionelectrode can be greater than the area of any of the surface electrodes.

According to one aspect of the embodiments, the connection electrode canbe trapezoidal in cross section, with an upper part having a smallerarea than a lower part, the upper part being further from the metal basethan the lower part.

According to another aspect of the embodiments, the connectionelectrodes includes a plurality of connection electrodes that aresymmetrical about a first axis that is parallel to the side portions,and symmetrical about a second axis that is perpendicular to the firstaxis.

According to another aspect of the embodiments, the connectionelectrodes include at least two connection electrodes formed at opposingsides of the metal base with the semiconductor chip sandwiched betweenthe at least two connection electrodes.

According to another aspect of the embodiments, a semiconductor chip canbe mounted in a region close to one side of the metal plate and all ofthe connection electrodes can be formed in a region close to an oppositeside of the metal plate.

According to another aspect of the embodiments, at least one connectionelectrode can include at least two connection electrodes formed in aninner region of the bottom portion, and positions of the at least twoconnection electrodes and positions of the surface electrodes aresymmetrical about two axes that are perpendicular to one another.

According to another aspect of the embodiments, solder balls can beformed on the at least one of the connection electrodes and one of thesurface electrodes.

According to the present invention, a semiconductor device can have thesame essential advantages of conventional approaches like that of FIGS.13(a) and 13(b), which include excellent heat dissipating capability,reduced size, low cost, and enhanced mechanical strength. However, thepresent invention can also protect electrodes of a semiconductor chipfrom excessive impact or force when the semiconductor device is mountedface down on a mounting substrate, as connection electrodes can be at ahigher level than surface electrodes of the semiconductor chip. Thus,mechanical damage to the semiconductor device can be avoided.

Moreover, according to the present invention, a gap can be providedbetween surface electrodes of a semiconductor chip and corresponding padportions of a mounting substrate.

As a result, the squashing of solder supplied thereto can be prevented.This can stop solder from leaking out to peripheral portions of asemiconductor device and causing a short circuit with an adjacent padportion, or cause other inconveniences. Further, with such a gap, theamount of solder between surface electrodes of a semiconductor chip andcorresponding pad portions of a mounting substrate can be of theappropriate thickness, therefore connection reliability with respect tomechanical stress can be improved. This can improve solderingreliability.

As noted above, according to a semiconductor device of the presentinvention, connection electrodes can be formed by selectively cutting ofupper edges of both side portions on a metal base. The side portions canthen be bent to stand upward from a bottom portion of the metal base.This can make it possible to make connection electrodes with a smallerarea than electrodes of semiconductor chip by shortening the length ofthe connection electrodes. Further, heat capacity for the connectionelectrodes can be reduced, while mechanical strength can be essentiallymaintained, as connection electrodes can be continuous with sideportions. Reliability in soldering to a mounting substrate can beimproved. In particular, a more suitable soldering connection to theconnection electrodes and electrodes of the semiconductor chip can bemade, even when pad portions of a mounting substrate for such electrodesare the same size.

In the present invention, connection electrodes can be arranged to besymmetrical in a longitudinal direction with respect to the sideportions, or in a direction perpendicular with the longitudinaldirection, or in both such directions. In such an arrangement, asemiconductor device can be placed on a mounting substrate in stablefashion when soldered thereto. As a result, heat can be more uniformlyconducted during a solder operation, and butting force can be moreevenly distributed among the connection electrodes. This can improveconnection reliability.

In the present invention, grooves can be formed in a surface of a metalplate between a bottom portion and side portions. Such an arrangementcan make it possible to form side portions with a relatively high degreeof precision.

Further, because connection electrodes can be formed by bending upperedges of side portions outward, an area for soldering connectionelectrodes to a mounting substrate can be large, even though a metalbase is formed from a metal plate. This can make low resistanceconnections possible.

In the present invention, a semiconductor device can include a metalbase with connection electrodes formed by an increased thickness inselected regions of a metal plate. Such connection electrodes can have asmaller area than surface electrodes of a semiconductor chip. Such anarrangement can increase soldering reliability, as the heat capacity ofthe connection electrodes can be reduced. This can make the solderamount for the connection electrodes substantially equal to the solderamount for the surface electrodes of a semiconductor chip in a mountingoperation.

Connection electrodes can be trapezoidal in cross section, with an upperpart thereof having a smaller area than a lower part thereof. This canenhance the mechanical strength of the connection electrode and improvethe reliability in soldering of the mounting substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a semiconductor device according to afirst embodiment of the present invention.

FIG. 2 is an exploded perspective view of a semiconductor deviceaccording to a first embodiment.

FIGS. 3(a), 3(b) and 3(c) are a plan view, front view, and right sideview, respectively, of the semiconductor device of FIG. 1.

FIG. 4 is a conceptual diagram for illustrating a method ofmanufacturing semiconductor device according to various embodiments ofthe present invention.

FIG. 5 is a perspective view illustrating a mounting structure for asemiconductor device according to one embodiment of the presentinvention.

FIGS. 6(a) and 6(b) are a perspective and enlarged side cross sectionalviews, respectively, of a semiconductor device according to a secondembodiment of the present invention.

FIGS. 7(a) and 7(b) are a perspective and enlarged side cross sectionalviews, respectively, of a semiconductor device according to a thirdembodiment of the present invention.

FIG. 8 is a perspective view of a semiconductor device according to amodified example of the first embodiment.

FIGS. 9(a) and 9(b) are perspective views of a semiconductor deviceaccording to modified examples of a second and third embodiment,respectively.

FIGS. 10(a) and 10(b) are perspective views of a semiconductor deviceaccording to other modified examples of a third embodiment,respectively.

FIGS. 11(a), 11(b) and 11(c) are a perspective view, enlarged side crosssectional view, and plan view, respectively, of a semiconductor deviceaccording to a fourth embodiment of the present invention.

FIG. 12 is a perspective view of one example of a conventionalsemiconductor device.

FIGS. 13(a) and 13(b) are perspective views of other examples ofconventional semiconductor devices.

FIG. 14 is a perspective view of yet another example of a conventionalsemiconductor device.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention will be described with reference to a number ofdrawings. FIG. 1 is a perspective view of a first embodiment in whichthe present invention is applied to a semiconductor device D with ametal-oxide-semiconductor field effect transistors (MOSFET) chip. As iswell known in the art, a MOSFET can be one type of insulated gate fieldeffect transistor.

FIG. 2 is a partially exploded perspective view of the device of FIG. 1.FIGS. 3(a), 3(b) and 3(c) are a plan view, front view, and right sideview, respectively, of the device of FIG. 1.

Referring now to FIGS. 1, 2 and 3(a) to 3(c), a first embodiment mayinclude a metal base 10 formed from a copper, German silver (e.g., analloy of copper, zinc, nickel), or other metal plate having asubstantially rectangular shape. Both sides of such a plate can be bentto a 90° angle to have a predetermined width. Such a shaping can resultin a metal base 10 having a flat bottom portion 11 and side portions 12standing upright to the left and right of the bottom portion 11.

A metal base 10 can also include shallow and narrow grooves 13 formed onthe surface of the metal base 10 that run along the border between thebottom portion 11 and side portions 12. Such narrow grooves 13 make itpossible to bend both side portions 12 with a high degree of precision.

In addition, side portions 12 can have notches 14 at intervals alongtheir lengths. Notches 14 can be obtained by cutting a center portionand both ends from each of the side portions 12. A depth of such notchescan be essentially half the overall height of the side portions 12. Twoparts of each side portion 12, situated between notches 14 where sideportions 12 maintain a full height, can be considered convex portions(e.g., 15).

Convex portions (e.g., 15) can serve as drain connection electrodes 15.Each of drain connection electrodes 15, when measured in a longitudinaldirection, can have a length less than or equal to a diameter of acircular gate electrode 7 and source electrode 8. A gate electrode 7 andsource electrode 8 will be described at a later point herein. In otherwords, the length of each drain connection electrode 15 can be eachequal to, or somewhat shorter than that of gate electrode 7 and sourceelectrode 8.

A semiconductor chip 1 can be mounted on the top face of the bottomportion 11 with a die bonding material 20, such as a silver paste. Asemiconductor chip 1, as shown in a partial cutaway view in FIG. 2, caninclude a MOSFET element 3 formed on the principal surface of the chip 2that can be cut out of silicon or another semiconductor material(typically in wafer form). A metal layer can be formed all over the rearsurface of the underside of the chip 2 and can serve as a drainelectrode 4. Also, an insulating layer 5 covering the element 3 can beformed on the top face of the chip 2.

Contact holes 6 can be opened in the insulating layer 5, and metallayers connected to element 3 can be formed in contact holes 6 to form agate electrode 7 in one contact hole, and a source electrode 8 inanother. A gate electrode 7 and source electrode 8 can be formed to havea circular shape and can be placed side by side in a longitudinaldirection of both side portions 12. In the particular example shown, agate electrode 7 and source electrode 8 can have the same shape and samearea.

A semiconductor chip 1 can be mounted with a drain electrode 4 on a rearsurface in direct contact with a top face of a bottom portion 11 of ametal base 10. With a semiconductor chip 1 thus mounted, positions ofgate electrode 7 and source electrode 8 can match the positions of drainconnection electrodes 15 formed in both side portions 12, with respectto a longitudinal direction.

Furthermore, as shown in FIG. 1 and FIG. 3(c), when the semiconductorchip 1 is mounted to a metal base 10, there can be a difference in levelbetween gate electrode 7 and source electrode 8 with respect to drainconnection electrodes 15. Such a level difference “d” can be obtained inthe example of FIG. 3(c) by subtracting a surface level of gateelectrode 7 and source electrode 8 from a surface level of drainconnection electrodes 15. Such a level difference “d” can be from 0 to0.1 millimeters (mm), preferably equal to or less than 0.05 mm. As butone example, a level difference “d” can be about 0.03 mm.

Having described a semiconductor device D, a method of manufacturingsuch a device will now be described with reference to FIG. 4. FIG. 4 isa conceptual diagram for illustrating the manufacturing method.

Referring to FIG. 4, an elongated metal plate M of a predeterminedthickness can be formed. Such a metal plate M can be formed from copper,German silver, or another suitable metal.

In a step S1, an elongated metal plate M can be fed in the longitudinaldirection, and successively punched with a punching machine to formnotches M1 along the length of a metal base. Metal bases are thus linkedto one another in the longitudinal direction by linking pieces M2.Linking pieces M2 can be can be cut off in a later step to facilitateseparation of one individual semiconductor device from another.

At this point, shallow and narrow grooves (e.g., item 13 of FIGS. 1, 2,3(c)) can be formed on the surface of metal plate M at a border betweena bottom portion 10 and both side portions 12 of metal base 10.

Such a punching step S1 can punch out portions of a center and both endsof side portions 12 of the metal base 10 in a longitudinal direction.This can form notches 14 having a predetermined length and a width thatis essentially half the total width of the side portions 12.

In a step S2, a bending machine can bend portions of metal plate Moutside narrow grooves 13, so that such portions stand at essentially90°, with respect to a bottom portion 11. Such a step S2 can result in abottom portion 11 between narrow grooves 13, with side portions 12standing up to the left and right of the bottom portion 11. The bendingof both side portions 12 can be guided by narrow grooves 13, therebyfacilitating the bending process for such side portions, and providingfor accurate dimensions.

As can be seen by the enlarged view of FIG. 3(c), bending of sideportions 12 can be accomplished without forming a curved face (R) on theinner walls of bent portions. Therefore, a bending position can beplaced closer to a semiconductor chip 1 that is to be mounted on a metalbase 10. This can result in a semiconductor device D that is smaller insize. Further, as also shown in the enlarged view of FIG. 3(c), if bothside portions 12 are bent so that side walls 13 a of narrow grooves 13abut a top face of bottom portion 11, position control for side portionscan be maintained, and a resulting height for both side portions 12 canbe established with a high degree of precision.

Still further, a bending arrangement like that detailed in the enlargedview of FIG. 3(c) can prevent deformation of drain connection electrodes15 and side portions 12 when mechanical stress is applied to sideportions 12 in a subsequent mounting step. In such a mounting step, twoportions on the upper surface of each side portion 12, situated betweennotches 14 (formed by a punching machine), can serve as drain connectionelectrodes 15. At the same time, side portions 12 can maintain a fullwidth.

In a step S3, a die bond material supplier can place a silver paste, orsome other die bond material, onto the surface of the bottom portion 11.

In a step S4, a mounting machine can position a semiconductor chip 1 ona surface of bottom portion 11. A semiconductor chip 1 can be cut from awafer W. When a semiconductor chip 1 is positioned on a bottom portion11, a drain electrode 4 on a rear surface of semiconductor chip 1 can bepressed against bottom portion 11. A semiconductor chip 1 can bepositioned in a mounting step such that a gate electrode 7 and sourceelectrode 8 are centered with respect to bottom portion. Further, in alongitudinal direction, a gate electrode 7 and source electrode 8 can bealigned with drain connection electrodes 15 on each side portion 12.

In a step S5, a curing machine can subject the structure to a heattreatment to cure (i.e., reflow) a die bond material 20, and therebymount semiconductor chip 1 to a bottom portion 11. At this point, aforce with which semiconductor chip 1 is depressed can be adjusted (orthe amount of die bond material 20 can be adjusted) to set a surfacelevel of drain connection electrodes 15 of both side portions 12 to behigher than a surface level of a gate electrode 7 and source electrode8. Such a surface level difference “d” can be about 0 to 0.1 mm. In thepresent example, “d” can be about 0.03 mm.

In a step S6, a separating machine can cut links M2 of metal plate Mwhich connect one metal base 10 to another in a longitudinal direction.

Following a step S6 manufacture of an individual semiconductor device D,shown in FIG. 1, can be completed.

Referring now to FIG. 5, a mounting arrangement for a semiconductordevice D is shown in a perspective view. A semiconductor device D can bemounted face down onto a mounting substrate 30 on which a circuitpattern 32 is formed. A circuit pattern 32 can have pad portionscorresponding to the positions of the gate electrode 7, source electrode8, and drain connection electrodes 15. A mounting substrate 30 can be aninsulating plate 31 with a copper foil, or the like, patterned to formcircuit pattern 32. In the example of FIG. 5, circuit pattern 32includes a gate pad portion 33, a source pad portion 34, and drain padportions 35.

When mounting a semiconductor device D to a mounting substrate 30,solder (not shown) can be printed, in advance, onto the surface of padportions 33, 34 and 35 on mounting substrate 30. Semiconductor device Dcan then be positioned so that its top face opposes the surface of themounting substrate, with gate electrode 7, source electrode 8 and drainconnection electrodes 15 facing corresponding pad portions 33, 34 and35, respectively. At this point, solder reflow can be carried out tosolder the electrodes of the semiconductor device D to their respectivepads. In this way, mounting can be completed.

As described above, in a semiconductor device D of this embodiment, ametal base 10 can have a surface area that is slightly larger than asemiconductor chip 1, and a thickness of the device can be approximatelythe sum of the thickness of the semiconductor chip 1, and the thicknessof metal base 10. Moreover, in such an arrangement there can be no needto bond a metal wire, or the like, to the semiconductor chip 1 and thedevice is not sealed in resin. Thus, the present invention can provide asemiconductor device having a reduced size and thickness. Further, sucha device can also include favorable heat dissipating capabilities asmetal base 10 can function as a heat sink.

When mounting a semiconductor device D of the above embodiments to amounting substrate 30, a surface level of drain connection electrodes 15can be set higher than a level of gate electrode 7 and source electrode8 of semiconductor chip 1. Therefore, as a semiconductor device D is putface down on a mounting substrate 30, a drain connection electrode 15alone can abut the mounting substrate 30. This can save a gate electrode7 and source electrode 8 from excessive impact, or abutting force, andthus prevent mechanical damage to a semiconductor chip 1.

In addition, in the above arrangement, an appropriate distance can becreated between a gate electrode 7 and a source electrode 8 andcorresponding pad portion 33 and 34, respectively, so as to not squashsolder supplied to these portions. Squashing solder can result in solderleaking out to peripheral portions to thereby short circuit a padportion 33 or 34 with an adjacent pad portion 35, or cause some otherinconveniences. In addition, such a separation distance can ensure thatthe connecting solder has a sufficient thickness to improve connectionreliability against mechanical stress. Soldering reliability can thus beimproved.

In the above arrangements, a length of a drain connection electrode 15on both side portions 12 can be substantially shorter than the totallength of a metal base 10, while at the same time being essentiallyequal in length to a gate electrode 7 and source electrode 8.Accordingly, an area of drain connection electrodes 15 can be smallerthan the area of a gate electrode 7 and a source electrode 8. This canresult in drain connection electrodes 15 with a lower heat capacity thanconventional arrangements. Consequently, when such a device is solderedin a mounting operation, the amount of solder for drain connectionelectrodes 15 can be almost the same as the amount of solder for a gateelectrode 7 and a source electrode 8 of a semiconductor chip 1.

Because drain connection electrodes 15 have a lower heat capacity, thetemperature needed to solder such electrodes can be less thanconventional arrangements, and thermal damage to a semiconductor chip 1can be reduced. Further, a lower soldering temperature can preventsolder from running up drain connection electrodes 15, a gate electrode7 and a source electrode 8, that might otherwise occur. This can producea more suitable soldering arrangement.

As noted above, the amount of solder needed for drain connectionelectrodes 15, a gate electrode 7 and a source electrode 8, can beessentially even. Making the amount of solder essentially even in thisfashion can facilitate the design of a solder supplying mask of amounting substrate 30 and/or inspection of a solder paste print result,or the like.

Further, by providing more uniform heat capacity, mounting operationscan be more effective as the timing for the melting and/or solidifyingsolder can be more uniform, thus preventing positioning failures thatcould otherwise occur.

It is noted that while the area of the drain connection electrodes 15can be reduced, as their overall length is shortened with respect toconventional approaches, such drain electrodes 15 are arranged side toside on the longitudinal direction, and remain integral to theirrespective side portions 12. Therefore, the mechanical strength of drainconnection electrodes 15 is not believed to be impaired.

In the above embodiments, drain connection electrodes 15 can besymmetrical in a longitudinal direction of both side portions 12. Drainconnection electrodes 15 are also symmetrical on a width direction ofthe semiconductor chip 1 that is perpendicular the longitudinaldirection. Accordingly, when a metal base 10 is placed face down on asurface of a mounting substrate 30 during a mounting operation, theevenly arranged drain connection electrodes 15 can abut a mountingsurface 30. This can make it possible to stably place the semiconductordevice D on a mounting substrate 30 for soldering. As a result, heat canbe uniformly conducted during soldering, and an abutting force on asemiconductor device D can be evenly distributed among the drainconnection electrodes 15. This can improve connection reliability. Thatis, in one particular embodiment, four drain connection electrodes 15are provided that are symmetrical in both a longitudinal direction andwidth direction of a metal base 10, to thereby provide a highly stabledevice.

In the manufacture of semiconductor device D of this embodiments, asshown in FIG. 4, both side portions 12 can be formed by bending alongnarrow grooves 13 formed in metal plate M. Drain connection electrodes15 can be formed in both side portions by punching. As mentioned before,such an approach can make is possible to improve the reliability of thesemiconductor device D over conventional approaches by giving drainconnection electrodes 15 highly precise dimensions, and the like.Furthermore, the only processing that may be needed includes punching,bending and press cutting of a metal plate M. As a result, manufacturingcan be relatively simple and advantageously lower in price than otherconventional approaches.

FIG. 6(a) is a perspective view of a semiconductor device according to asecond embodiment. FIG. 6(b) is an enlarged partial cross section of thesemiconductor device of FIG. 6(a). The example of FIGS. 6(a) and 6(b)shows a semiconductor device that can include a MOSFET, similar to afirst embodiment. Components of this embodiment that are equivalent tothose of the first embodiment will be denoted by the same referencecharacter.

In this embodiment, the shape of a drain connection electrode of a metalbase 10A can be modified to provide one drain connection electrode 15Aon each side portion 12. Each drain connection electrode 15A can beformed substantially in the center, in the longitudinal direction, ofthe corresponding side portion 12. That is, drain connection electrodes15A can be formed by making a substantially central portion (in thelongitudinal direction) of each side portion 12 taller than a remainingportion of the side portion 12. This can form a projecting piece 16. Theprojecting piece can then be bent outward at a predetermined point at a90° angle, so that the projecting piece is essentially horizontal. Thehorizontally-bent portion of the projecting piece 16 can serve as adrain connection electrode 15A.

In the example of FIG. 6(a), the horizontal portion of the projectingpiece 16 that serves as a drain connection electrode 15A can have asquare shape. A length of a side of such a square can be close to thatof a square that would be inscribed within a circle of circular gateelectrode 7 and source electrode 8 of the semiconductor chip 1.

In the embodiment of FIGS. 6(a) and 6(b), like previous embodiments, asemiconductor chip 1 can be mounted to the surface of a bottom portion11 of a metal base 10A. A semiconductor chip 1 can be essentiallyidentical to that of the first embodiment, with a drain electrode 4 on abottom surface of semiconductor chip 1 being mounted to a metal base 10Awith a die bond material. A surface of semiconductor chip 1 can have agate electrode 7 and a source electrode 8. Once a semiconductor chip 1is mounted, a surface level of drain connection electrodes 15A can behigher than that of gate electrode 7 and source electrode 8. Such adifference in height can be about 0 to 0.1 mm, preferably about 0.3 mm.

Like the first embodiment, in a semiconductor device of FIGS. 6(a) and6(b), a metal base 10A can have a slightly larger surface area than asemiconductor chip 1, and an overall thickness of such a device can bethe sum of the thickness of the of the semiconductor chip 1 and themetal base 10A. Moreover, there is no need to bond a metal wire, or thelike, to a semiconductor chip 1, and the device does not have to besealed in resin.

In this way, a second embodiment can provide a semiconductor device thatcan be reduced in size and thickness, and when mounted, can exhibitadvantageous heat dissipating capability because metal base 10A canfunction as a heat sink.

When a semiconductor device like that of FIGS. 6(a) and 6(b) is mountedto a mounting substrate 30, like that shown in FIG. 5, drain connectionelectrodes 15A can be easily soldered, as their area can be smaller thanthat of a gate electrode 7 and source electrode 8. Such a smaller areacan translate into lower heat capacity during a solder reflow. A smallerarea for drain connection electrodes 15A can result from making sides ofthe square shape far shorter than an overall length of a metal base 10A.

In one particular arrangement, one side of the square of a drainconnection electrode 15A can be the length of a square inscribed withina circle of gate electrode 7 and source electrode 8. Further,corresponding to such an arrangement, a mounting substrate can includedrain connection electrode pads (shown differently as 35 in FIG. 5)having the same essential dimensions as a gate electrode pad portion 33and a source electrode pad portion 34. Therefore, drain connectionelectrodes 15A can be contained within corresponding pad portions inmost cases.

It is also noted that while an area of drain connection electrodes 15Acan be made smaller than that of a gate electrode 7 and source electrode8, a lower portion of drain connection electrodes 15A can be integral toa corresponding side portion 12, which can run along an entire length ofa metal base 10A. As a result, a mechanical strength of a drainconnection electrode 15A can be enhanced.

Furthermore, because a surface of drain connection electrodes 15A can behigher at a higher level than gate electrode 7 and source electrode 8,mechanical damage to a semiconductor chip 1 that might otherwise occurin a mounting operation can be prevented. In addition, solderingreliability of gate electrode 7 and source electrode 8 are suitableimproved.

The embodiment of FIGS. 6(a) and 6(b) can be formed by metal plateprocessing similar to that previously described, yet resulting drainconnection electrodes 15A can have a larger area than those of thepreviously described embodiments. Thus, this embodiment may be lessadvantageous will respect to reducing heat capacity of such drainconnection electrodes. However, such an approach can result in a largercontact area between drain connection electrodes 15A and a correspondingpad portion (e.g., 35) of a mounting substrate 30. Thus, this embodimentmay have an advantageously lower drain connection resistance.

In this way, a mounting reliability in drain connection electrodes canbe improved substantially over other conventional semiconductor deviceapproaches.

FIG. 7(a) is a perspective view of a semiconductor device according to athird embodiment. FIG. 7(b) is an enlarged partial cross section of thesemiconductor device of FIG. 7(a). While a metal base of a semiconductordevice of FIGS. 6(a) and 6(b) can be formed by bending, a metal base 10Bin this arrangement can be formed by etching or forging.

A metal base 10B can be rectangular and can be a little wider than asemiconductor chip 1. A metal base 10B can have a bottom portion 11B. Arectangular mesa-like convex portion 17 can be formed on a surface ofeach side of a bottom portion 11B. A convex portion 17 can serve as adrain connection electrode 15B. Like a drain connection electrode 15A ofa second embodiment, a drain connection electrode 15B can be positionedin the center, with respect to a longitudinal direction, of a bottomportion 11B. A drain connection electrode 15B can have substantially thesame are as a drain connection electrode 15A. However, when viewed incross section, can have a trapezoidal shape, so that the area of a lowerpart is a little larger than that of an upper part.

With a semiconductor chip 1 mounted, a surface level of drain connectionelectrode 15B can be higher than a gate electrode 7 and source electrode8 of a semiconductor chip 1 by about 0 to 0.1 mm, preferably about 0.03mm.

A semiconductor device according to the embodiment of FIGS. 7(a) and7(b) can have the same thickness as the other embodiments, and thereforeprovides a reduced thickness as compared to conventional approaches. Inaddition, such a semiconductor device can be reduced in size as a bottomportion 11B of a metal base 10B can have substantially the same area asthe above other embodiments. Furthermore, a metal base 10B can functionas a heat sink to give this semiconductor device an advantageous heatdissipating capability.

A semiconductor device according to the embodiment of FIGS. 7(a) and7(b) can be mounted to a mounting substrate in a manner similar to thefirst and second embodiments. A drain connection electrode 15B can beintegral to a bottom portion 11B of a metal base 10B, thus making itsheat capacity greater than that of gate electrode 7 and source electrode8. However, a drain connection electrode 15B heat capacity can remainsomewhat reduced, as its area can be less than that of a gate electrode7 and source electrode 8, and it can have a trapezoidal cross sectionalshape. Accordingly, any difference in the amount of solder needed fordrain connection electrodes 15B versus gate electrode 7 and sourceelectrode 8, can be limited. Thus, the amount of solder needed can beevened out among the drain connection electrodes 15B, gate electrode 7,and source electrode 8.

In addition, in the embodiment of FIGS. 7(a) and 7(b), because a surfaceof drain connection electrodes 15B can be higher than a gate electrode 7and source electrode 8, mechanical damage to a semiconductor chip 1 thatcould occur during a mounting operation can be prevented, and thereliability of a soldering of a gate electrode 7 and source electrode 8can be improved.

Still further, in the embodiment of FIGS. 7(a) and 7(b), a drainconnection electrode 15B can be trapezoidal in cross section, with alower part that can be integral to a bottom portion 11B of metal base10B. This can provide substantial mechanical strength to the drainconnection electrodes 15B. This too, can help to improve mountingreliability.

In the above embodiments, a semiconductor device can be mounted to amounting substrate by forming solder balls, solder bumps or the like, ona gate electrode, source electrode, and drain connection electrodes. Theuse of solder balls can reduce mounting failures, as solder balls can beeasier to use than pad-like electrodes. In addition, the height ofsolder balls can create a distance from a mounting substrate surface,resulting in less flux components adhering to a surface of asemiconductor chip during a mounting operation. Thus, decreases inreliability arising from flux related corrosion can be prevented.

One example of a solder ball arrangement for a semiconductor device D,like that of the first embodiment, is shown in FIG. 8. In FIG. 8, solderballs 21 can be formed on a gate electrode 7 and source electrode 8. Insuch an arrangement, a semiconductor device D can be formed with sideportions 12A on both sides of metal base 10 that are increased inheight. Thus, drain connection electrodes 15 can be slightly taller thanas solder balls 21 above the surface of gate electrodes 7 and sourceelectrodes 8. As a result, drain electrodes 15 can be at a level ofabout 0.03 mm higher than a level of solder balls 21. In this way, theabove advantages of solder ball mounting can be obtained by utilizingsolder balls 21 and drain connection electrodes 15 to mount asemiconductor device to a mounting substrate.

One example of a solder ball arrangement for a semiconductor device likethat of the second embodiment is shown in FIG. 9(a). FIG. 9(b) shows anexample of applying solder balls to a third embodiment. In FIGS. 9(a)and 9(b), solder balls 21 can be formed on electrodes 7, 8, 15A, and15B. The corresponding semiconductor device can then be mounted to amounting substrate by a hot press-fit utilizing such solder balls.

In both embodiments of FIGS. 9(a) and 9(b), a surface level of solderballs 21 on rain connection electrodes 15A and 15B can be higher than asurface level of solder balls 21 f gate electrodes 7 and sourceelectrodes 8. Such arrangements can be maintained even if die thicknessvaries, as shown by the following examples.

Referring now to FIG. 10(a), if a relatively thick semiconductor chip 1Ais mounted to a metal base 10B like that of a third embodiment, therecan be a substantial difference in the surface level of a gate electrode7 and source electrode 8 with respect to drain connection electrodes15B. However, solder balls 21 can be formed on drain connectionelectrodes 15B having a diameter that corresponds to such a differencein surface level. This can make is possible to mount such asemiconductor device face down on a mounting substrate.

Conversely, as shown in FIG. 10(b), if a height of drain connectionelectrodes 15B′ is substantially greater than a thickness of asemiconductor chip 1, solder balls 21 can be formed on a gate electrode7 and source electrode 8 having a diameter that corresponds to thedifference in surface level. In this case, solder balls 21 can be givena surface level that is different than drain connection electrodes 15B′.

Referring once again to FIG. 4, to mount solder balls according to thevarious teachings set forth above, a process can include a step S7. In astep S7, a solder ball mounting machine can be placed down stream of amounting step S4 (or mounting machine). In particular, after asemiconductor chip 1 is mounted to a metal base 10, solder balls 21 areplaced on predetermined electrodes by a solder ball mounting machine(step S7) and then subjected to a reflow step by a curing machine (stepS5). In this way, solder balls can be mounted on electrodes of asemiconductor device. Solder bumps are also applicable in stead ofsolder balls.

FIG. 11(a) is a perspective view of a semiconductor device according toa fourth embodiment of the present invention. FIG. 11(b) is an enlargedpartial cross section of the semiconductor device of FIG. 11(a). Likethe first embodiment, this embodiment shows the application of thepresent invention to a MOSFET. In this embodiment, a metal base 10C canbe formed from a rectangular metal plate. Such a metal base 10C can havean area that is approximately twice the size of semiconductor chip 1.

As shown in FIG. 11(a), a semiconductor chip 1 can be mounted in aregion that is close to one side of a bottom portion 11C of metal base10C. Two drain connection electrodes 15C can be integrally formed inregion close to the other side of bottom portion 11C. A semiconductorchip 1 can be identical to a semiconductor chip 1 of a first embodiment.Thus, a semiconductor chip 1 can include a drain electrode 4 on a rearsurface that is mounted to the surface of bottom portion 11C with a diebond material, or the like. Further, a semiconductor chip 1 can includea front surface that includes circular gate electrode 7 and sourceelectrode 8.

As shown in FIGS. 11(a) and 11(b), drain connection electrodes 15Cformed on one side of a bottom portion 11C of a metal base 10C can havea circular, mesa-like shape. In one approach, drain connectionelectrodes 15C can be formed by etching of forging a metal plate thatconstitutes metal base 10C. A circular mesa-like shape can have adiameter slightly smaller than that of circular gate electrode 7 and/orsource electrode 8. Further, a diameter of drain connection electrodes15C can be a little bit larger in a lower region than an upper region toprovide a trapezoidal shape when viewed in cross section (e.g., FIG.11(b)).

Referring now to FIG. 11(c), two drain connection electrodes 15C can besymmetrically arranged with respect to edges of a bottom portion 11C ofmetal base 10C.

More particularly, a distance from drain connection electrodes 15C to aleft side edge (when viewing FIG. 11(c)) can be essentially the same asthe distance of an upper drain connection electrode 15C to top edge, anda distance of a lower drain connection electrode 15C to a lower edge.

In addition or alternatively, drain connection electrodes 15C can besymmetrical with respect to gate electrode 7 and source electrode 8. Forexample, as shown by dashed lines in FIG. 11(c), a center of gateelectrode 7, a center of source electrode 8, and the centers of drainelectrodes 15C can from a square. Further, such a square can beconcentric with respect to metal base 10C.

In the particular embodiment of FIGS. 11(a) and 11(b), drain connectionelectrodes 15C can have a surface level essentially equal to that of agate electrode 7 and a source electrode 8. That is, a surface leveldifference between such electrodes can be essentially 0 mm.

A semiconductor device of the embodiments of FIG. 11(a), 11(b) or 11(c)can have essentially the same thickness as the above described firstthrough third embodiments. Therefore, such a device can provideadvantageously reduced thickness as compared to some conventionaldevices. However, the embodiments of FIG. 11(a), 11(b) or 11(c) can havea larger area than other embodiments, as a metal base 10C can beessentially twice the size of a semiconductor chip 1 (as opposed toessentially the same size in the other embodiments). However, such alarger size metal base 10C can serve as a larger heat sink once thedevice is mounted. Thus, a fourth embodiment may provide enhanced heatdissipation characteristics.

When mounting a semiconductor device FIG. 11(a), 11(b) or 11(c) to amounting substrate, all electrodes can be soldered under almostidentical conditions. This is because drain connection electrodes 15Ccan be circular like a gate electrode 7 and a source electrode 8 ofsemiconductor chip 1. Even though drain connection electrodes 15C areintegral to a metal base 10C, and thus can present a larger heatcapacity than a gate electrode 7 and a source electrode 8, a diameter ofdrain connection electrodes 15C can be slightly smaller than a gateelectrode 7 and a source electrode 8, and can be trapezoidal in crosssection. As a result, the amount of solder needed for mounting can bemore even among the electrodes, and the need for disadvantageously hightemperatures can be eliminated. Thus, the reliability of a solderingconnection for drain connection electrodes 15C and/or gate electrode 7and source electrode 8 can be improved.

Still further, in the event drain connection electrodes are equidistantfrom the sides of a metal base 10C, drain connection electrodes 15C havethe same heat capacity. As a result, a heat capacity balance in acircumferential direction around the drain connection electrodes 15C canbe essentially uniform. This can be effective in improving theuniformity of solder reflow for drain connection electrodes 15C.

Still further, because drain connection electrodes 15C are situated in aregion within metal base 10C, solder can be prevented from running upside walls of a metal base 10C in a mounting operation.

Even further, when drain connection electrodes 15C, a gate electrode 7and a source electrode 8 are symmetrically arranged, stability of ametal base 10C during a mounting operation can be enhanced. This canequalize soldering conditions among the electrodes, further improvingthe solder connections for such electrodes.

It is additionally noted that because a surface level of drainconnection electrodes 15C, a gate electrode 7 and a source electrode 8can be essentially equal, a semiconductor device will be placed on amounting substrate in a stable fashion during soldering operation. Alongthese same lines, drain connection electrodes 15 that are integral to ametal base can provide connections with advantageous mechanicalstrength. This too can improve mounting reliability.

In a fourth embodiment, like that shown in FIGS. 11(a) and 11(b), solderballs can be formed on drain connection electrodes 15C, a gate electrode7 and a source electrode 8 (although an illustration of such anarrangement is not included).

Further, while drain connection electrodes of a third and fourthembodiment have been shown with trapezoidal shapes in cross section,such electrodes may have other shapes, such as prism-like orcylindrical, as but two examples. However, in such arrangements, drainconnection electrodes are integral to a metal base, and no groove isallowed between the drain connection electrodes and the metal base, inorder to provide a continuous structure.

Still further, while particular examples of a fourth embodiment haveshown drain connection electrodes 15C, a gate electrode 7, and a sourceelectrode 8 arranged in to a square, other embodiments may havedifferent arrangements. As but one example, similar operational effectscan be obtained by arranging such electrodes in some other grid pattern.

The first through third embodiments have shown examples in which a drainconnection electrode can be taller than gate electrode and sourceelectrode by a predetermined amount. However, this characteristic shouldnot be construed as limited to only the disclosed embodiments. Accordingto the present invention, such a feature can be applied to different,otherwise known semiconductor devices, to thereby prevent mechanicaldamage and/or improve soldering reliability to drain connectionelectrodes or other electrodes.

It is understood that if etching is employed to form a metal base, likethose of the third and fourth embodiments, such a method may not be asadvantageous as other embodiments that utilize bending. Nevertheless,such etching approaches are relatively easy to realize as a metal plateneed only be etched in a thickness direction, and drain connectionelectrodes can be relatively simple shapes. Needless to say, if forgingis employed, such a manufacturing step can be as easy to employ asbending.

The above embodiments have illustrated examples of a semiconductordevice applied to a MOSFET semiconductor chip. However, the presentinvention could be applied to other types of devices, including but notlimited to a bipolar transistor, a diode, an integrated circuit (IC), orthe like.

As has been described, according to the present invention, connectionelectrodes a device can be set at a higher level than a gate electrodeand source electrode of a semiconductor chip. Therefore, mechanicaldamage to a semiconductor chip, that could otherwise occur when thedevice is mounted face down, can be avoided. Further, such a resultingdifference in height between electrodes of a semiconductor chip and amounting substrate can increase the reliability of a solder connectionto such electrodes.

According to the present invention, a semiconductor device can include ametal base with a bottom portion and side portions formed by bending.Connection electrodes can be formed by selectively cutting off upperedges of the side portions. Accordingly, the area of such connectionelectrodes can be made smaller than electrodes of a semiconductor chipby shortening the length of such connection electrodes. This can reducethe heating capacity of the connection electrodes, even out the amountof solder among the electrodes, and raise the soldering reliability forsuch electrodes. At the same time, thermal damage to a semiconductorchip can be avoided.

Still further, lower parts of connection electrodes can be integral to ametal base to ensure mechanical strength. Furthermore, a symmetricalarrangement of connection electrodes can make it possible to place ametal base onto a mounting substrate in a stable fashion during asoldering operation. This can improve soldering reliability.

According to the present invention, connection electrodes can be formedby bending remaining upper edges of side portions of a metal baseoutward. Such connection electrodes can have a smaller area thanelectrodes on a corresponding semiconductor chip. Therefore, despite thefact that connection electrodes are formed by processing a metal plate,because such electrodes are bent outward, connection electrodes for amounting substrate can provide a relatively large and low resistanceconnection.

According to the present invention, a metal plate can include connectionelectrodes formed by areas of partially increased thickness in a bottomportion thereof. An area of such connection electrodes can be smallerthan the area of electrodes on a corresponding semiconductor chip.Therefore, a heat capacity of such connection electrodes can be reduced,and the amount of solder can be evened out among the electrodes.Connection electrodes can be trapezoidal in shape when viewed in crosssection, with a lower part having a larger area than an upper part. Thiscan enhance mechanical strength of such connections, and can raise thereliability of soldering connections to such electrodes to a mountingsubstrate. If surfaces of connection electrodes are set higher thansurfaces of a semiconductor chip electrodes, mechanical damage to asemiconductor chip in a mounting operation can be prevented, and thesoldering reliability for such connections can be improved.

While various particular embodiments set forth herein have beendescribed in detail, the present invention could be subject to variouschanges, substitutions, and alterations without departing from thespirit and scope of the invention. Accordingly, the present invention isintended to be limited only as defined by the appended claims.

1. A semiconductor device, comprising: a metal base having a bottomportion formed from a metal plate and at least one connection electrodethat extends upward from at least a part of the bottom portion to afirst surface level, the at least one connection electrode for mountingthe semiconductor device to a mounting surface; and a semiconductor chipmounted to the bottom portion of the metal base having surfaceelectrodes at a second surface level, the first surface level beinghigher than the second surface level by a predetermined amount, and thesurface electrodes for mounting the semiconductor device to the mountingsurface.
 2. The semiconductor device of claim 1, wherein: thepredetermined amount is greater than 0 millimeters and less than orequal to 0.1 mm.
 3. The semiconductor device of claim 1, furtherincluding: solder balls or bumps formed on the at least one of theelectrodes selected from the group consisting of the at least oneconnection electrode and the surface electrodes.
 4. The semiconductordevice of claim 1, wherein: the semiconductor chip is an insulated gatefield effect transistor (IGFET) having a drain electrode formed on arear surface in direct electrical contact with the bottom portion of themetal base so that the at least one connection electrode is a drainconnection electrode, and the surface electrodes include a gateelectrode and source electrode for the IGFET.
 5. The semiconductordevice of claim 1, wherein: the predetermined amount is greater than0.01 millimeters and less than or equal to 0.05 mm.
 6. The semiconductordevice of claim 1, further including: a die bond material between thebottom portion of the metal base and the semiconductor chip.
 7. Thesemiconductor device of claim 6, wherein: the die bond material includesa metal substance providing an electrical connection between a bottomconnection electrode of the semiconductor chip and the metal plate. 8.The semiconductor device of claim 7, wherein: the metal substanceincludes silver.
 9. The semiconductor device of claim 1, wherein: themetal base includes grooves along the bottom portion where theconnection electrode extends upward.
 10. The semiconductor device ofclaim 1 wherein: the at least one connection electrode includes a firstconnection electrode and a second connection electrode.
 11. Thesemiconductor device of claim 10 wherein: the first and secondconnection electrodes are separated by a notch.
 12. The semiconductordevice of claim 11 wherein: the notch has a depth below the firstsurface level of essentially one-half the distance between the firstsurface level and a surface of the bottom portion.
 13. The semiconductordevice of claim 1, further including: solder balls or bumps formed on atleast one of the surface electrodes.
 14. The semiconductor device ofclaim 1 further including: a notch in the metal plate formed on bothsides of the at least one connection electrode.
 15. The semiconductordevice of claim 14 wherein: the notch has a depth below the firstsurface level of essentially one-half the distance between the firstsurface level and a surface of the bottom portion.
 16. The semiconductordevice of claim 1, further including: an insulating layer formed on asurface of the semiconductor chip including surface electrodes.
 17. Thesemiconductor device of claim 16, further including: contact holesformed in the insulating layers to expose the surface electrodes. 18.The semiconductor device of claim 1, wherein: the metal plate includescopper.
 19. The semiconductor device of claim 1, wherein: the metalplate includes zinc.
 20. The semiconductor device of claim 1, wherein:the metal plate includes nickel.